Hydrogenation of cyclic hydrocarbon diolefins to cyclic hydrocarbon olefins

ABSTRACT

A process is described whereby a diolefin is selectively hydrogenated to an olefin in the presence of a palladium base catalyst by adding to the reaction mixture an aqueous solution of a zinc salt such as zinc acetate wherein the ratio of water/zinc is at least 1/1 by weight.

United States Patent [191 Morelli et a1.

[ Dec. 31, 1974 HYDROGENATION OF CYCLIC HYDROCARBON DIOLEFINS TO CYCLIC HYDROCARBON OLEFINS Inventors:

Assignee:

Filed:

Appl. No.:

Morello Morelli, San Donato Milanese; F ortunato De Marco, Milan, both of Italy Snamprogetti, S.p.A., San Donato Milanese, Italy July 24, 1973 Foreign Application Priority Data July 27, 1972 US. Cl...... 260/666 A, 260/666 R, 260/677 H, 260/683.2 Int. Cl. C07c 5/04 Field of Search 260/666 A, 667

References Cited UNITED STATES PATENTS Italy 27492/72 Haensel 260/6 67 2,728,713 12/1955 Kearby et al. 260/667 3,369,052 2/1968 Howell et a1 260/666 A 3,408,415 10/1968 Dovell et al. 260/666 A 3,418,386 12/1968 Hayes 260/666 A 3,433,842 3/1969 3,751,497 8/1973 Schwerdtel et al. 260/666 A Primary Examiner-Delbert E. Gantz Assistant Examiner-Veronica OKeefe Attorney, Agent, or FirmRalph M. Watson, Esq.

6 Claims, No Drawings HYDROGENATION OF CYCLIC HYDROCARBON DIOLEFINS TO CYCLIC HYDROCARBON OLEFINS The present invention relates to a process for the selective hydrogenation of diolefin hydrocarbons to olefin hyrdocarbons.

It is already known that it is possible to hydrogenate diolefin compounds in the presence of palladium catalysts: however in the past a mixture of olefin and saturated compounds was obtained with an uncontrolled selectivity in olefin compounds.

To reach satisfactory results and to stop the subsequent hydrogenation of the olefin compound to saturated compound, it has been-proposed to partially deactivate the palladium catalyst, by impregnation or coprecipitation with salts of Pb, Zn, Hg, Cd, Th, Sn etc.

However said impregnation or coprecipitation methods are difficult to be practically carried out, in that the deactivation conditions of the catalyst (temperature, deactivating salt concentration, operating time) are very critical; as a matter of fact, by operating under conditions even slightly different from the optimum ones, catalysts are obtained which are either non selective or wholly deactivated.

It is also known that to obtain a high selectivity catalyst it is necessary that the impregnation or coprecipitation treatment be carried out at a rather high temperature (80 to 100C), which is, on the other hand, particularly disadvantageous in the case of supported catalysts.

We have now found that it is possible to obtain selectivity as close as to 100 percent in the hydrogenation of diolefin compounds to olefin compounds, by operating at relatively low temperature or in any case at a temperature ranging from' C to 60C, by employing conventional palladium catalysts, possibly supported for instance on calcium carbonateor barium sulfate and by adding to the reaction mixture an aqueous solution of zinc salt. Therefore by operating according to the present invention it is possible to obtain selectivities as high as 100 percent without it being necessary to subject the palladium catalyst to the hot impregnating or coprecipitating operations which'are very expensive and complicated because the zinc is added continuously as an aqueous solution to the hydrogenation mixture. Beside the above practical and economical advantage, the present invention represents a further advance in that the life of the catalyst employed according to the invention, at the same selectivity values, is longer than the life of the known deactivated catalysts.

According to the present invention the passage of I material to be hydrogenated and zinc salt on the catalyst in the course of the continuous tests can be effected for many times while obtaining always very good selectivity. The anion ofthe zinc salt has no importance as to the selectivity, but it is preferable that the salt have a high solubility in water. In this connection the chloride, sulfate, nitrate, acetate and oxalate are quite suitable.

The amount of salt can vary from 0.0] to 5 percent and preferably from 0.01 to 2 percent by weight with respect to the diolefin compound.

The minimum amount of water necessary for the good course of the reaction is such as to be sufficient to dissolve the zinc salt under the reaction conditions.

It is therefore necessary that there be a ratio water/- zinc salt of at least l/l by weight.

On the other hand it is advisable to utilize a water/- zinc salt ratio not higher than 50/] in order to have a satisfactory reaction rate.

In the absence of water the hydrogenation of the diolefin compounds is not stopped at the lst stage, i.e., at the formation of olefine compounds, but it goes on up to the production of saturated compounds.

It is preferable to add to the reaction mixture an amine compound, generally ammonia, in very low amounts, preferably lower than 0.5% by weight with respect to the diolefin compound, even though higher amounts, up to 20 30 percent do not negatively effect the reaction.

The present invention can be applied to continuous or discontinuous processes in a wide range of tempera-- ture, for instance, between 20C and 60 instance C, and 0t izrsss tstfqriastanse f m. U9 .ZQW Q Phq It is to be noted that the amount of the salt, which is to be added to the reaction mixture, depends, within the abovementioned ranges, the reaction rate, i.e., on the hydrogen pressure and the temperature, and also on the efficacy of stirring.

By operating according to the present invention, the absorption of hydrogen from the reaction mixture stops after one of the double-bonds has been hydrogenated to a simple bond, then, by letting the reacted mixture at the reaction conditions also for relatively long times, a further hydrogenation does not substantially occur.

The present invention will be better illustrated by the following operative examples.

EXAMPLE 1 Cyclopentadiene was hydrogenated in the presence of 2 percent by weight of a Pd base catalyst on CaCO as catalyst carrier (5% Pd) at the temperature of 30C. 0.2 percent of ammonia, 0.2 percent of dehydrated zinc acetate and 0.4 percent by weight of water were added into an autoclave kept under stirring by means of a stirrer consisting of a hallow shaft for letting hydrogen be recirculated. The hydrogen pressure was 5 kg/cm The course of reaction was controlled by gaschromatography analysis performed on samples drawn at regular intervals.

After minutes hydrogen absorption was no'more noted and the selectivity as cyclopentene (cyclopentene)/(cyclopentene cyclopentane) percent by moles was 99.4. Starting cyclopentadiene was practically absent. After an other 90 minutes under the reaction conditions the selectivity was higher than 99 percent.

EXAMPLE 2 We operated according to'example l but the water amount was l percent. After the disappearance of starting cyclopentadiene, the selectivity as cyclopentene of the obtained product was 99.2 percent and'was practically constant also after a long time during which the product remained at the reaction conditions.

7 EXAMPLE 3 We operated according to example I but no water was added. v

The selectivity as cyclopentene, after the dicyclopentadiene disappearance, was 89 percent; by keeping the product under the reaction conditions for 30 minutes again, the selectivity decreased up to 74 percent because of the formation of cyclopentane and, after 30 minutes again, the selectivity decreased to 60 percent.

EXAMPLE 4 and 5' Isoprene and pentadiene were subjected to hydrogenation according to Example 1.

After the total disappearance of the diolefins, mixtures were obtained of olefine isomers at selectivities respectively of 99.1 and 98.7.

What we claim is:

l. A process of hydrogenating a cyclic hydrocarbon diolefin by contacting said cyclic diolefin with hydrogen in the presence of a palladium base catalyst, wherein the improvement comprises increasing the selectivity of the hydrogenation of said cyclic hydrocarbon diolefin to cyclic hydrocarbon olefin by adding to the hydrogenation mixture an aqueous solution of a zinc salt having a ratio of water/zinc of at least 1/1 by weight.

2. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the amount of said zinc salt is from 0.01 percent to 5 percent by weight of the cyclic hydrocarbon diolefin.

3. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the hydrogenation is carried out at temperatures ranging from 20 to 60C and at pressures between 1 and 50 atmospheres.

4. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the hydrogenation is carried out in the presence of an amine compound in the amount of not more than 0.5 percent by weight of the cyclic hydrocarbon diolefin.

5. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 4, wherein the amine com pound is ammonia.

6. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the zinc salt is a member of the group consisting of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate and zinc oxalate. 

1. A PROCESS OF HYDROGENATING A CYCLIC HYDROCARBON DIOLEFIN BY CONTACTING SAID CYCLIC DIOLEFIN WITH HYDROGEN IN THE PRESENCE OF A PALLADIUM BASE CATALYST, WHEREIN THE IMPROVEMENT COMPRISES INCREASING THE SELECTIVITY OF THE HYDROGENATION OF SAID CYCLIC HYDROCARBON DIOLEFIN TO CYCLIC HYDROCARBON OLEFIN BY ADDING TO THE HYDROGENATION MIXTURE AN AQUEOUS SOLUTION OF A ZINC SALT HAVING A RATIO OF WATER/ZINC OF AT LEAST 1/1 BY WEIGHT.
 2. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the amount of said zinc salt is from 0.01 percent to 5 percent by weight of the cyclic hydrocarbon diolefin.
 3. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the hydrogenation is carried out at temperatures ranging from 20* to 60*C and at pressures between 1 and 50 atmospheres.
 4. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the hydrogenation is carried out in the presence of an amine compound in the amount of not more than 0.5 percent by weight of the cyclic hydrocarbon diolefin.
 5. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 4, wherein the amine compound is ammonia.
 6. A process of hydrogenating a cyclic hydrocarbon diolefin according to claim 1, wherein the zinc salt is a member of the group consisting of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate and zinc oxalate. 